node.js 后台将file文件发到java后台用MultipartFile接收

在Node.js向Java后端发送文件时，由于它们运行在不同的技术栈下，你需要中间件来转换和传递文件。常见的做法是先将Node.js生成的文件流转换成Base64字符串，然后发送给Java，Java后端再从Base64解码恢复原始文件。这里以Express为例：

**Node.js（发送文件至Java）**

首先，安装必要的模块，如`multer`用于处理文件，`axios`用于HTTP请求：

npm install multer axios

然后，在Node.js中处理文件并将Base64编码发送给Java：

const express = require('express');
const multer = require('multer');
const axios = require('axios');

const app = express();
const upload = multer({ dest: 'uploads/' });

app.post('/upload-to-java', upload.single('file'), async (req, res) => {
  try {
    const fileBuffer = await new Promise((resolve) => {
      req.file.stream.pipe(buffer()).on('finish', () => resolve(buffer()));
    });

    const base64Data = Buffer.from(fileBuffer).toString('base64');
    
    const response = await axios.post(
      'http://your-java-backend-url/upload-file', // 替换为实际的Java API URL
      { fileBase64: base64Data }, // 将文件内容作为Base64字段
      { headers: { 'Content-Type': 'application/json' } }
    );

    res.json(response.data);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

app.listen(3000, () => console.log('Server started on port 3000'));

**Java（接收并解码Base64文件）**

在Java方面，你需要一个能接受Base64编码文件的API。这里是一个简单的Spring Boot示例，假设使用了`spring-boot-starter-web`和`jackson-databind`：

import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

@RestController
public class FileUploadController {

    @PostMapping("/upload-file")
    public void receiveFile(@RequestParam("fileBase64") String fileBase64, HttpServletResponse response) throws IOException {
        byte[] decodedBytes = Base64.getDecoder().decode(fileBase64);

        Path filePath = Paths.get("path/to/save/file", "received_file.txt"); // 替换为实际保存路径
        Files.write(filePath, decodedBytes);

        response.setStatus(HttpServletResponse.SC_OK);
        response.getWriter().println("File received and saved successfully");
    }
}